This invention relates to trap sensing circuits for signalling an alarm which will indicate to a marine trapper that an animal is in the trap.
The present state of the art of marine trap sensing systems has not overcome the problems of false signal output due to the high saline condition of the underwater environment. This desirable feature, while recognized, has not been achieved by the prior art through the use of circuits and components in the electrical circuitry of the sensing system itself. The disadvantages which are produced by false signals require the marine trapper to be present in the area and they also have a tendency to scare away the animals as the traps are lifted from the water and replaced with greater frequency thus disturbing the trap environment and producing a smaller harvest of animals.
A new and improved marine trap alarm with a sensing system that includes an electrical current producing source such as a battery, a normally open pair of contacts with at least one movable contact to be actuated by an animal to be trapped, and a trap sensing circuit connected to the open contacts. The trap sensing circuit includes a true comparator and a silicone controlled rectifier. The true comparator includes an operational amplifier that is controlled by critical discrete cmponent values that are engineered to neutralize input current flow bridging the contacts by way of the high saline fluid environment, which would otherwise be an input current flow to the operational amplifier under high saline fluid environment to eliminate false output signals to an alarm or indicator. When the normally open pair of contacts is closed by the weight of the animal, a differential potential then exists between the inverting and noninverting inputs of the operational amplifier causing the output voltage to rise and trigger the latching circuit to set off the alarm.